In recent years, it is common to order and purchase various products through the Internet. After receiving such orders through the Internet, sellers pack products having various sizes in boxes to send the products to consumers. When such products are packed in boxes, if various kinds of boxes are used according to the size of each of the products in light of transportation efficiency, it requires large costs to manage such boxes and choose an appropriate box from such boxes for each packing.
In order to overcome this problem, JP Publication 2009-7029 discloses a box which has foldable side walls so that the size of the box can be changed to several kinds of sizes.
However, since the size of such a box as disclosed in JP Publication 2009-7029 cannot be freely (steplessly) adjusted, it is impossible to make the gap inside the box as small as possible and improve transportation efficiency.